Centrifugal pumps have a shaft mounted impeller imparting energy to a fluid entering from a low pressure inlet port and exiting a high pressure outlet port. The shaft is sealed against unintended fluid flow to the atmosphere by a mechanical seal mounted in the pump housing. The fluid being pumped is primarily a coolant for engine cooling. In addition, the same coolant is used to cool and lubricate the mechanical seal. Seal deterioration can result due to debris in the fluid and also from elevated temperatures encountered in operation due to inadequate seal lubrication by the coolant.
In U.S. Pat. No. 5,713,719, Feb. 3, 1998, by the present inventor and another, there is disclosed a centrifugal pump of a type in which the inlet is centrally located on the front face of the pump housing (i.e., an axial entry pump) modified to include a self flushing feature for improved seal life. The self flushing feature of the patent provides a secondary fluid flow path wherein some of the energized pump fluid is drawn into a region containing the seal and out through apertures in the impeller. The positive flow of fluid through the seal region enhances seal cooling and debris removal.